A rapidly unfolding intervention in Atlanta provides a rare opportunity to advance health services research for a vulnerable population: poor Black drug users. The Atlanta Housing Authority (AHA) is relocating all 5,000 residents of seven concentrated public housing communities to homes spread across Atlanta. Past research indicates that relocates tend to move to census tracts that have markedly better socioeconomic and healthcare environments than their original tracts;however, their social networks and support systems shrink after they move. The AHA relocations thus offer a rare opportunity to deepen scientific knowledge about the ways in which neighborhood, network, and social support factors shape Black drug users'healthcare access and health. Mining this opportunity will advance several NIDA priority areas, but is predicated on rapid funding of this project: three AHA communities (the "BBT" communities) have already begun the relocation process, and four others (the "HHRP" communities, which include Herndon Homes, Hollywood Court, Roosevelt, and Palmer) will begin to relocate in 2009. Traditional NIH funding cycles are too slow to realize the opportunities presented by the AHA relocations. While we presently have funds to gather pre-relocation data on 150 BBT residents, this sample size is insufficient to explore multilevel hypotheses. A team of two new investigators with a history of collaboration is thus seeking Time Sensitive R21 funds to achieve the following aims: (1) For 200 Black drug-using residents of the four HHRP communities, describe pre-relocation neighborhood, network, and social support characteristics (e.g., spatial access to drug treatment, drug network size, recovery support), and residents'(a) access to and retention in drug treatment, and primary care access;(b) drug use patterns;and (c) sexual risk and sexually transmitted infection (STI) status. We will integrate spatial, survey, and biological data to achieve Aim 1. (2) For 100 ex-residents of the two communities that will relocate first (Herndon Homes and Hollywood Court), assess participants'post-relocation status on the variables listed in Aim 1, and pre-/post-relocation changes in these variables. (3) For the total sample of 350 residents of the HHRP and BBT communities, conduct exploratory cross-sectional analyses of pre-relocation relationships between neighborhoods, network and social support characteristics and participants'(a) access to and retention in drug treatment, and access to primary care;(b) drug use patterns;and (c) sexual risk behaviors and STI infection status. We will also initiate preliminary analyses of the 100 Herndon Homes and Hollywood Court participants'pre-/post-relocation data to explore how changes in exposures relate to changes in outcomes. We will seek R01 funds to conduct a longitudinal study of the 350-member cohort that will test hypotheses generated by the R21. This longitudinal R01 study will establish the direction of relationships identified in the R21 in a sample of sufficient size to draw firm statistical conclusions about topics of major scientific import to NIDA.